The
traditional meaning of comprise is "to include all parts"
or "is made up of".

For example,

a) The circus comprises lions,
elephants, and clowns. (active voice)

b) Lions, elephants, and clowns are
comprised by the circus. (passive voice)

But comprise is often incorrectly used in
place of constitute or compose.

For example,

c) The plant is comprised of leaves, stems,
and roots. (passive voice)

(should read: Leaves,
stems, and roots are comprised by the plant.)

d) Leaves, stems, and roots comprise the
plant. (active voice)

(should read: The plant comprises leaves,
stems, and roots.)

Because they support the traditional, narrower
definition of the word comprise, grammarians consider c) and d)
to be incorrect.

Stylists dislike c) and d) because those
uses indicate ignorance of the traditional definition and more importantly,
those uses seem inflated. In c) and d), comprise can easily be replaced
by the more common verbs compose, consist, and constitute.

For example,

e) The plant consists of (or is composed
of) leaves, stems, and roots.

d) Leaves, stems, and roots constitute
the plant.

Scientists and academics often use comprise
and usually use it incorrectly. Why would anyone use comprise in place
of the simpler verbs? --see Politics and the English
Language and also ask yourself when you last heard your aunt Martha
or uncle Louie use comprise.